Between the july 14th and october 12th snapshots are taken of the amount of Nxt that is in your wallet.
If you have let say 10.000 Nxt for this whole period you will get 10.000 Ardor.
But if you have 10.000 Nxt for 1/2 the period you get 1/2 of 10.000 Ardor.

If you get Nxt now you can still get 2/3 of that amount in Ardor.